Polishing pads used for polishing semiconductor devices and the like are generally classified into hard ones and soft ones. Hard polishing pads are prepared mainly based on the dry method in which a urethane prepolymer is formed by chain-extension. Soft polishing pads are prepared mainly based on the wet method in which a urethane resin solution is coagulated in a coagulation bath and dried. Recently, polished workpieces have been required to have high flatness and uniformity, and soft polishing pads have increasingly been used in a finish polishing step and the like.
Especially, it is particularly desirable that a finish polishing step of bare silicon, semiconductor devices, and magnetic disks be excellent in polishing amount and polishing flatness, and be reduced in formation of polishing scratches (also referred to as defects). In a conventional finish polishing step, a polishing pad having a wet urethane resin film as a polishing layer has been used (see, for example, Patent Documents 1 and 2).
However, conventional wet polishing pads still have a problem of a high tendency to cause polishing scratches.